The present invention generally relates to transducer microsystems and assembling methods therefore, and in particular to transducer microsystems comprising electromechanical transducer components built in a flexible manner.
Microsystems are in the following regarding systems of components with sizes in the order of centimeters or less. Transducers are components or devices that transduces one energy form to another. Normally the transducers are divided in actuators and sensors even though there are many that can operate both as sensors and actuators. A sensor transforms an external stimulus to another useful energy form, preferably an electrical signal. An actuator essentially makes the opposite. A signal, preferably electrical, is transformed into any other useful energy form. Among the useful energy forms or external stimuli can be included mechanical, acoustic, electrostatic, electromagnetic, magnetic, optical, thermal, biological, biomedical, medical, chemical and atomic force energy. An electromechanical transducer is thus an actuator, transforming an electrical signal into a mechanical motion, and/or a sensor, transforming a mechanical motion into an electrical signal. Depending on application, the energy forms can be further subdivided e.g. mechanical transducers are typically divided into subgroups such as piezoelectric, electrostrictive, shape memory, inertial and resonant effects.
Examples of transducer microsystems are e.g. piezoelectric micromotors, ink jet print heads, accelerometers and pressure sensors packaged with their integrated circuits. A transducer microsystem normally consists of a number of microcomponents, such as e.g. electronic components, micromechanical components, electromechanical components, electrical leads, connectors, structural members etc. The production of a microsystem thus normally involves the assembling of a number of parts, most of which are very small. Monolithic microcomponents are normally assembled in a package and thereafter assembled in one or many levels of carriers. Assembling, mechanically and electrically, of tiny parts is a technically complicated matter, in particular when time, and thereby production costs, and space are limited. One common drawback from a commercial point of view is thus that the assembling techniques of the systems become the main technical obstacle.
A large number of Microsystems are available today, and the general development tendency is to further reduce the sizes. The above assembling problems thus becomes even more accentuated, since members serving to connect different parts increases the total size of the system. One way to reduce these problems are expressed in the wish to reduce the total number of components and integrate as many functions as possible in each component. However, a final assembling procedure will always remain.
A transducer microsystem according to prior art normally comprises a number of transducer components attached to some main structural element. A typical example is e.g. the crash sensor SA30, manufactured by SensoNor a.s, Norway. Another example may e.g. be found in xe2x80x9cPackaging of Pressure Sensor Chips for Microsystem Applications: Technology and Testxe2x80x9d, by A. Gxc3x6tz, C. Canxc3xa9, A. Morrissey and J. Alderman, Proceedings of xe2x80x9cThe ninth Micromechanics Europe Workshop, NME""98xe2x80x9d, p. 272-275. In order to function, the transducer components normally have to be pressed or supported against internal or external forces in the system. The carrier and/or the package functions as the main structural member in the system. In the case of e.g. an electromechanical motor, an internal pressing force has to exist. The pressing force gives rise to a frictional force, by which the movable part may be moved.
The main structural element thus serves several purposes. The main structural member should keep the components in position, relative to some reference points. The main structural member should also support the components against external forces, protect the components against mechanical damage and serve as a general casing. The main structural member also often provide an attachment member for the whole system to be connected mechanically to other systems, i.e. a mechanical connection point or points. For Microsystems, the main structural member normally also supply internal forces between different parts of the system, as described above. The transducer microsystem further comprises electrical connectors, wires and electronics, supporting the transducer components.
A general problem with microsystems according to prior art is that the assembling is time consuming, technically difficult and increases the total system size. Microsystems according to prior art also exhibit problems regarding tolerances, assembling precision and adjustment possibilities.
An object of the present invention is thus to reduce the number of components necessary for assembling a transducer microsystem. A further object of the present invention is to provide a more efficient and flexible assembling method, which at the same time allows for high precision.
The above objects are provided by a device and a method according to the enclosed claims. In general words, the present invention makes use of a flexible printed circuit board, not only as a mounting support for electronics components and wiring, but also for mechanically supporting various components as well as acting as a main structural member for the entire microsystem. All components necessary for a microsystem may be mechanically mounted onto a flexible printed circuit board, which finally is elastically deformed to a required final shape. In the final shape, the resilience of the flexible printed circuit board is used to apply elastic forces on selected transducer components of the microsystem.
In preferred embodiments, the flexible printed circuit board is provided with geometrical structures, which are possible to use for locking and/or adjustment of the final deformation of the flexible printed circuit board. The mechanical attachment of the components for the microsystem to a flexible printed circuit board takes preferably place with the flexible printed circuit board in a substantially two-dimensional state, whereby a final shape of the microsystem is achieved by deforming the flexible printed circuit board.